Pharmacogenomics and drug response

Following pioneer work in the early 20th century, the era of molecular pharmacogenomics started with the cloning of a polymorphic gene encoding the drug-metabolizing enzyme cytochrome P450-2D6. Today, recent conceptual and methodological advances in genomics allow a much broader approach to elucidating inheritance patterns in drug response and identification of functional polymorphisms, that affect drug response, has become a key issue. Despite recent euphoria about potential applications of pharmacogenomic principles, currently available pharmacogenomic data have had modest overall impact on the routine of drug therapy. Most data were derived from single gene approaches for select drug metabolizing enzymes with extreme phenotypes. Data on genetic determinants of drug distribution, absorption and response, however, are scarce and it seems that most events in the dose-response cascade follow a complex interplay of environmental factors with several genes encoding proteins in multiple pathways. Thus, there is great need for clinical studies on genotype-phenotype and gene environment interactions, based on multiple gene approaches. Major challenges also relate to practical aspects of clinical pharmacogenomic studies, e.g. appropriate data handling, selection of appropriate study designs and control groups and issues of prediction accuracy. To move to a clinically useful and predictive level in pharmacogenomics, much work remains to be completed. Nevertheless, it can be anticipated that for select drugs, pharmacogenomics may lead to a shift from the current strategy of developing medications for a statistically optimized fraction of patients to a strategy that aims to provide tailored medications for genetically diverse patients.